For the treatment of the impairment of memory by different causes such as multiple infarcted dementia, senile dementia, Alzheimer's dementia, sequelae of cerebral injury and cerebral apoplexy and the like, various agents such as cerebral vasodilators, agents for improving cerebral metabolism, nootropic agents and the like have been proposed, but the satisfactory improvement could not be obtained by any of these agents.
As the extensive research with respect to the compounds showing the satisfactory improvement of the impaired brain function, the present inventors found that 4-piperidinecarboxamide derivatives having N-[(2-oxo-1-pyrrolidinyl)-acetyl]-peptide side chain at 1 position improve the impaired brain function.